1. Field of the Invention
The present invention relates to the field of wireless communication, more particularly to a method and an apparatus for repeating wireless signals bidirectionnally and synchronously.
2. Description of the Related Art
With the improvement of the communication technology, not only the conventional Frequency Division Duplex (FDD) wireless communication system such as Global System for Mobile communication (GSM), and series standards (IS95) of narrow band CDMA(code division multiple access) system, ect., have developed very rapidly, but also the Time Division Duplex(TDD) wireless communication system are applied more widely because of the flexible frequency allocation without allocating paired frequency and the simple system devices. In the TDD wireless communication system, receiving and transmitting are performed respectively in different time slots in the same frequency channel or carrier wave to ensure that receive and transmit channel or uplink and downlink are seperated by the time difference.
In the FDD system, in order to expand the coverage area and avoid the occurrence of some blind areas in the system, wireless signals emitted from a base station and terminal devices are amplified by repeaters, and then the amplified signals are repeated. Since wireless transmission signals emitted from the base station and terminals are signals having different frequencies in FDD system, filters or duplexers can be used conveniently for repeaters to realize the separation between signals emitted from the base station and terminals, so that the bidirectional repeat can be realized. A block diagram of a repeater in conventional FDD system is shown in FIG. 1. Wireless signals emitted from the base station are emitted to the required coverage area through air after the frequency selection and amplification complete. Similarly, wireless signals emitted from terminals in coverage area are emitted to the base station after the frequency selection and amplification complete. Such bidirectional repeating performed simultaneously realizes the isolation between wireless signals emitted from the base station and terminals according on the frequency difference between signals emitted and received and on the attenuation of different frequency by duplexer, so that repeating wireless signals emitted from the base station and terminal devices bidirectionally and synchronously can be realized without applying sequential control to wireless signals.
In the TDD system, wireless transmission signals from the base station and terminals adopt same frequency and are distinguished only by the different time slot, thus bidirectional and synchronous repeating of these signals can't be realized by using the above repeator applied in the TDD system and must adopt novel design methods and apparatuses.
Method and apparatus for increasing the transmission distance of wireless communication devices are disclosed in Chinese Patent Application No. 98126224.4, wherein the apparatus comprises two diveces: the second one is used to generate clock signals at two operating rates for circuits used in frame synchronization of wireless interface, one of said two operating rates being lower than reference frequency and the other being higher, so that switching data in the TDD mode can be realized by means of adjusting time quantum of receive, storage and transmit. However, interferences with other users can occurr in the multiuser system by means of adjusting time quantum of receive storage and transmit. Also, a TDD repeater for CDMA is disclosed in another Chinese Patent Application No. 96196621.1, wherein, the TDD repeater receives the spread spectrum signals discontinuously, amplifies these signals and repeats the data in preceeding time slot until the following time slot by delaying them for a predetermined amount. The method intends to repeat data in this time slot until the next time slot by delaying signals greatly. When the switching intreval between receiving and transmitting signals is relatively longer, larger delays are needed, and it is difficult to utilize Surface Acoustic Wave (SAW) filter and results in the occurence of certain errors in fixed delays. At the same time, the inconsistency of the wireless resource between the allocated and the applied actually will occur.
During implementing repeating signals bidirectionally and synchronously, inferences, delay errors, etc., may occurred when using the above technologies. Therefore, the prior art can not satisfy the demands of repeating signals bidirecitonally and synchronously and results in difficulties in increasing coverage area and preventing occurrence of coverage blind areas in the TDD system.